Four-party-line telephone system.



-No'. 782,376. PATENTED FEB. 14, 1905. G. BABGOGK.

FOUR PARTY LINE TELEPHONE SYSTEM. APPLIOATION HLED HOV.14, 1903.

I l v Ty UNITE STATES GARRISON BABCOCK, OF CHICAGO, ILLINOIS, ASSIGNORTO STROIVIBERG- CARLSON TELEPHONE MANUFACTURING COMPANY, NEW YORK, ACORPORATION OF NEW YORK.

Patented. February 14, 1905.

ATENT OFFICE.

OF ROCHESTER,

FOUR-PARTY-LINE TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 782,376, dated February14, 1905.

Application filed November 14, 1903. Serial No. 181,127.

To all whom. it floaty concern:

Be it known that I, GARRIsoN BABoooK, a citizenof the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented-a certain new and useful Improvement in Four-Party-LineTelephone Systems,of which the following is a full, clear, concise, andexact description, reference being had to the accompanying drawing,forming a part of this specification.

My invention relates to telephone systems, and particularly tomultiparty telephone-lines and the apparatus associated therewith.

' My invention is particularly applicable to a form of four-partytelephone-line, which will be hereinafter more fully described.

In a large number of four-party telephonelines which have heretoforebeen employed it has been necessary toprovide a marginal adjustmentbetween telephone-bells located at subscribers substations and the linesignal or drop at the central telephone-exchange. In the use of such asystem it has been customary to provide a source of comparatively strongcurrents at the central oiiice adapted, when sent over thetelephone-line to ring the bell at some one of the four substationsconnected with a bimetallic line, these currents usually returning tothe signal-station by way of the ground. Each of the four subscriberssubstations has been provided with a generator adapted to send thecurrent over the line to throw the drop or actuate the signal at thecentral office. In order that the currents generated at the substationsshall not actuate the apparatus at each of the substations, two of thesubstation signaling devices, such as bells,

being connected between. one limb of the line and ground. and these twosignaling devices being oppositely polarized, so that one will beactuated upon the passage of currents of one polarity, while the otheris actuated only upon the passage of currents of opposite polarity. Theother two substation signaling devices have been connected between theother line-limb and ground, and these two signaling devices have alsobeen oppositely polarized, so as to be each actuated by currents ofopposite polarity. My invention is applicable to sucha system.

The principal objects of my invention are to provide means wherebystrong signalingcurrents may be generated at the substations withoutcausing an improper actuation of the signaling devices at any of thesubstations.

By means of my invention I am enabled to do away with marginaladjustment or difference of adjustment between the substation andcentral-office signaling devices.

By means of my invention a four-party line of the character describedmay be extended to a much greater length than has heretofore beenpossible. A slight leakage of the line will not injuriously affect theproper operation thereof.

A system constructed in accordance with signaling-generator at any oneof the substations.

My invention has another advantage in that it may readily and cheaply beapplied'to al-' most any of the well-known telephone linecircuits orsignaling-circuits employed at central exchanges.

In accordance with my invention I provide signaling devices at thesubstations as above describedthat is, two bells legged between eachline-limb and the ground and the two bells of each pair oppositelypolarized, so that one may be actuated by impulses in one direction andthe other actuated by impulses in the opposite direction. Asignal-generator is provided at each of the substations, 'each adaptedto generate currents of one polarity, l

the polarity of the current generated at any one substationcorresponding with the polarization of the signal-bell at thatsubstation. Each generator is adapted to be connected in bridge of thetelephone-line limbs insignaling the central oflice. Automatic or manualmeans is also provided in conjunction with each generator whereby theopposite linelimb from that to which the associated signalbell isconnected may be short-circuited to ground. The current set up by thegenerator at each substation is direct, so far as possible,asdistinguished from pulsating or alternating currents. The groundconnection, which is made at the generator at the time of signaling thecentral ofiice, produces a path through the associated signal-bell,whereby the actuation of the generator causes this bell to produce asingle tap. The generator will not cause an actuation of the other bellat any substation which is legged to the same linelimb, for the reasonthat this bell will be oppositely polarized, and no current will findits way to and through the signal-bells connected with the otherline-limb, for the reason that one line-limb is short-circuited toground, whereby the bells connected to that line-limb areshort-circuited, and thereby prevented from operating.

My invention will be more clearly understood by reference to theaccompanying drawmg.

1 have illustrated the telephone-line comprising limbs l and 2, whichlead from the central station to the substations b, 0, (Z and a. At thecentral exchange the line-limbs l and 2 terminate in the tip and sleevesprings of the jack 3, with which the contacts 4 and 5 normally makeconnection, these contacts being connected with a drop 6 or othersuitable form of signal. I have not illustrated the cord connectingapparatus used for the purpose of connecting this line with others, assuch apparatus is well known and understood by those skilled in the art.The apparatus is intended to operate in such a way that any one of thesubscribers may signal an operator at the central exchange withoutcausing an actuation of the signaling apparatus at any of the othersubstations and also in such a way that the operator may signal any oneof the subscribers without calling any other subscriber to his phone. Atsubstation b there is provided a polarized hell or signal 7, which wemay assume is positively polarized. At the same substation there is adirectcurrent generator 8, adapted to set up current of the polaritycorresponding with the polarization of the bell 7. In conjunction withthe generator there is a set of contactsprings 9, 10, and 11, adapted tobe automatically actuated upon the operation of the generator. Such aform of switching apparatus is well known and understood by thoseskilled in the art, and it will be understood that upon turning thecrank 12 of the generator the springs 9, 10, and 11 are automaticallyconnected together. The spring 9 is connected -with the ground. Thecontact-spring 11 is connected with the line-limb 2.

A well-known type of local-battery telephone set is shown at 14, thistelephone set being adapted 'to be connected in bridge of the line bythe removal of receiver 15 from the switch-hook 16, the removal of thereceiver at the same time causing a break in the bridging-circuitthrough the generator 8. There is provided at each of the substationssimilar signaling mechanism, that at substation c, which is connectedwith the linelimbs in the same way as that at substation 6, being,however, of opposite polarity, as indicated by the negative signs uponthe bell and generator. The apparatus at substations (Z and e isoppositely polarized, as indicated by the plus and minus signs, and'itwill be noted that the connections of the signaling-bells and generatorswith the line-limbs are just the reverse of what they are at substationsI) and 0. A subscriber, for instance, at substation b in signalingcentral office operates his directcurrent generator 8, whereby theterminals of the generator are connected across the linelimbs 1 and 2.Circuit can thereupon be traced from the generator through contactlB,switch-hook 16, line-limb 1, tip-spring ot the jack 3, contact 4,line-drop 6, contact 5, the sleeve-spring of the jack 3, line-limb 2,spring 11, spring 10, and from spring 9 back to the generator. lurrentstraversing this circuit cause an actuation of the drop 6 to notify thecentral-station operator that a connection is desired. A circuit fromthis generator at substation 5 can also be traced through the contact 13to switch-hook 16, to line-limb 1, thence through theelectromagnet-coils of the polarized signal-bell 7 at the samesubstation to ground and thence through springs 10 and 9 back to thegenerator. The bell 7 is adapted to be actuated by a pulsating currentof one polarity, that polarity corresponding with the direction of thedirect current set up by the generator 8 at the same substation. As thecurrent set up by the substation-generator is direct rather thanpulsating, there will be only one stroke of the bell 7, which is notobjectionable, and indeed has some advantages. If it were not for thefact that the line limb 2 is grounded at substation b upon the actuationof the generator 8, the current might be traced from the generator 8 toline-limb 2, thence to substations d and e, and through the signal-bellsat these stations to ground, thence through the ground to thesignal-bells at substations b and 0, and thus back to line-limb 1, whichis at'that time connected with the other terminal of the generator 8.The bell at substation 0 is negatively polarized, and therefore wouldnot be actuated by this current, nor would the bell located atsubstation d, as these bells are actuated only upon the passage of thecurrents in the negative direction. The positively-polarized bell atsubstation 6, however, would be actuated by operation of the generatorat substation Z), thereby notifying the subscriber at substation e thata call was being made. This actuation of another. subscribers 'bell isof course undesirable, for the reason thatit might call him to his phoneas inthe act of answering a signal intended for him, or it might serveto apprise him of the fact that a call is being initiated, whereupon hemight remove his telephone-receiver from the switch-hook and listen tothe conversation taking place. The actuation of the call bell or bellsat substations cZ and c is absolutely prevented, how ever, bygroundingthe line-limb 2 at substation 6 when a call is being initiatedfrom this substation. This ground connected to line limb 2 serves toshort-circuit the path from line-limb 2 to the call-bells at substationsd and c and thence through the call-bells at substations and c toline-limb 1 and thence to the other terminal of the generator. It willbe seen that connections of the switching mechanism associated with eachof the generators at the various substations are arranged so that thecall-bells which are connected with the other line-limb than that towhich the associated call-bell is connected will be shortcircuited andtheir operation thus prevented.

As will be well understood by those skilled in the art, there isprovided at the central station means whereby a series of pulsatingcurrents of either polarity may be connected between ground and eitherline-limb upon inserting a cord connecting-plug within the jack 3. Th usthe connection of a source of pulsating current between the ground andline-limb l at the central station will cause the actuation of thecall-bell at either substation b or substation 0, depending upon thepolarity of the signaling-current. The signals at substations (Z and awill neither of them be actuated, for the reason that they are connectedwith the other line-limb. In connecting up theapparatus the polarizationof the generator may be reversed by reversing the position 01 thepermanent magnets which form a part of the type of generator commonlyemployed for this purpose. For the reason that there is no tendency forthe calling-currents set up at a substation to cause the actuation ofsignalingbells at other substations the strength of thesecalling-currents may be made as great as is desirable, whereby thesystem may be employed ov-er lines having considerable length.

As will be understood by those skilled in the art, a manually-operatedswitch or pushbut-' ton may be substituted in place of the automaticgenerator-switch, as shown.

Other modifications of my invention may occur to those skilled in theart, and while I have shown the preferred form of my inven tion I do notwish to be limited to the precise construction herein set forth.

Having disclosed my invention, I claim as new and desire to secure byLetters Patent 1. In a telephone system, the combination with atelephone-line comprising two metallic limbs leading from an exchange toa series of substations, of a signal-bell at one substation connectedbetween one line-limb and a third conductor, a signal-bell at a secondsubstation connected between the second line-limb and said thirdconductor, an electrically-operated signal device at the centralexchangenormally connected between said line-limbs, a source of currentat the first said substation adapted when connected in bridge of theline-limbs to cause an actuation of the central-station signal device,and automatic means for closing a low-resistance path between the thirdconductor and the second line-limb when said source supplies current tosaid line.

2. In a telephone system, the combination with a telephone-linecomprising two metallic line-limbs leading from an exchange to a seriesof substations, a signal-bell at one substation connected between oneline-limb and a third conductor, a signal-bell at a second sub stationconnected between the second linelimb and said third conductor, anelectricallyoperated signal device normally connected in bridge of theline-limbs, a source of current at the first said substation, adaptedwhen connected in bridge of the line-limbs to cause an actuation of thesignal device, and means for closing-a low-resistance path between thethird conductor andthe second line-limb when said source suppliescurrent to said line.

3. In a telephone system, the combination with a telephone-linecomprising two metallic limbs leading from an exchange to a series ofsubstations, of an electrically-operated signal device at one of saidsubstations connected between one line-limb and a third conductor, anelectricallyroperated signal device at the second substation connectedbetween the second line-limb and said third conductor, an

electrically-operated signal device at the central station normallyconnected in bridge of saidQline-limbs, a source of current at the firstsaid substation adapted when connected in bridge of the line-limbs tocause an actuation of the central-station signal device, and automaticmeans for closing a low-resistance path between the third conductor andthe second line-limb when said source is connected to cause an actuationof the central-station signal device.

4. In a telephone system, the combination with a telephone-linecomprising two metallic limbs leading from a series of substations to'an exchange, of a signal-bell at one substation adapted to be actuatedby pulsating direct currents, said signal-bell being connected betweenone line-limb and a third conductor, a second signal-bell at the secondsubstation adapted to be actuated by pulsating currents of oppositepolarity, said second bell being connected between the second line-limband said third conductor, an electrically-operated signal device at thecentral exchange adapted for connection between the line-limbs,adirectcurrent signaling-generator at one of said substations adapted tobe connected in bridge of the line-limbs to cause an actuation of thesignal device at the central exchange, and automatic means for closing ashort-circuit path in shunt of one of said signal-bells when saidgenerator is connected in bridge of the linelimbs for signalingpurposes.

5. In a telephone system, the combination with a bimetallic lineextending by its limbs from a central exchange to a series ofsubstations, of a positively-polarized signal-bell and anegatively-polarized signal-bell connected between a third conductor andone of said linelimbs, a source of direct current adapted to beconnected in bridge of the line limbs, and means whereby the connectionof said source of current in bridge of said line-limbs automaticallyconnects each signal-bell in a direct shunt-path about said source.

6. In a telephone system, the combination with a bimetallic lineextending by its limbs from a central exchange to a series ofsubstations, of a signal-bell at one substation connected between athird conductor and one of said line-limbs, a source of current atanother substation adapted to be connected in bridge of the line-limbs,and means whereby the connection of said source of current in bridge ofsaid line-limbs automatically closes a lowresistance path between saidthird conductor and that line-limb to which said signal-bell isconnected to prevent actuation of said signalbell.

7. In a telephone system, the combination with a bimetallic lineextending by its limbs from a central exchange to a series ofsubstations, of a positively-polarized signal-bell and anegatively-polarized signal-bell connected between a third conductor andone of said linelimbs, a positively-polarized signal-bell and anegatively-polarized signal-bell connected between said third conductorand the second linelimb, a source of current of one polarity at onesubstation adapted to be connected in bridge of the line-limbs, andmeans whereby the connection of said source of current in bridge of theline-lim bs automatically closes a short-circuit shunt-path about thesignal-bells connected between one of the line-limbs and said thirdconductor at another substation to prevent actuation of saidsignal-bells.

8. In a telephone system, the combination with a bimetallic lineextending by its limbs from a central exchange to a series ofsubstations, of a positively-polarized, electricallyoperated signaldevice and a negatively-polarized, electrically-operated signal device,both connected between a third conductor and one of said linelimbs, apositively-polarized, electrically operated signal device and anegatively-polarized, electrically-operated signal connected between athird conductor and one of said line-limbs, a positively-polarized,electrically-operated signal device and a negatively-polarized,electrically-operated signal device connected between said thirdconductor and the second line-limb, a direct-current signaling-generatorassociated with one of said signaling devices at one of saidsubstations, and means whereby the actuation ofsaid generatorautomatically closes a low-resistance path between that line-limb towhich the associated signalingdevice is not connected and said thirdconductor.

10. In a telephone-exchange system, the combination with a bimetallictelephone-line extending by its limbs from an exchange to a series ofsubstations, of a signal-bell adapted to be actuated by pulsatingcurrents in a positive direction located at one substation and connectedbetween one line-limb and a third conductor, a second signal-belladapted to be actuated by pulsating currents in a negative directionlocated at a second substation and connected between the same line-limband said third conductor, a third signal-bell adapted to be actuated bypulsating currents in a positive direction located at a third substationconnected between said third conductor and the second line -limb, afourth signal -.bell adapted to be actuated by pulsating currents in anegative direction located at a fourth substation and connected betweensaid third conductor and said second line-limb, a direct-currentgenerator at each substation adapted for connection in bridge of theline-limbs, means whereby the actuation of each generator automaticallycloses a low-resistance path between said third conductor and thatline-'limb to which the signal-bell at the same substation is notconnected, the generator at each substation being of such polarity as tocause an actua tion of the signal-bell at the same substation, and anelectrically-operated signal device at ICC IIC

IIE

the central exchange, normally connected in bridge of said line-limbs.

11. In a telephone-exchange system, the Combination with a bimetallictelephone-line extending by its limbs from an exchange to a series ofsubstations, of a signal-bell adapted to be actuated bycurrents in apositive direction located at one substation and connected between oneline-limb and a third conductor, a second signal-bell adapted to beactuated by currents in a negative direction located at a secondsubstation and connected between the same line-limb and said thirdconductor, a

third signal-bell adapted to be actuated by currents in a positivedirection located at a third substation connected between said thirdconduetor and the second line-limb, a fourth signal-bell adapted to beactuated by currents in a negative direction located at a fourthsubstation and connected'between said third conductor and said secondline-limb, a direct-current generator at each substation adapted forconnection in bridge of the line-limbs, means whereby the actuation ofeach generator au tomatically closes a low-resistance path between saidthird conductor and that line-limb to which the signal-bell at the samesubstation is not connected, the generator at each substation being ofsuch polarityas to cause an actuation of the signal-bell at the samesubstation, and an electrically-operated signal device at the centralexchange, normally connected in bridge of said line-limbs.

12. In a telephone-exchange system, the combination with a bimetallictelephone-line extending by its limbs from an exchange to a series ofsubstations, of a signal-bell adapted to be actuated by currents in apositive direction located at one substation and connected between oneline-limb and a third conductor, a second signal-bell adapted to beactuated by currents in a negative direction located at a secondsubstation and connected'between the same line-limb and said thirdconductor, a third signal-bell adapted to be actuated by currents in apositive direction located at a third substation and connected betweensaid third con' ductor and the second line-limb, a fourth signal-belladapted to be actuated by currents in a negative direction located .at afourth substation and connected between said third conductor and saidsecond line-limb,'a direct-current generatorat each substation adaptedfor connection in bridge of the line-limbs, means whereby the actuationof each generator automatically closes a low-resistance path betweensaid third conductor and one line-limb, and an electrically-operatedsignal device at the central exchange normally connected tosaidlinelimbs.

13. In a telephone-exchange system, the combination with a bimetallictelephone-line extending by its limbs from an exchange toa series ofsubstations, of a signal-bell adapted to be actuated by pulsatingcurrents located at one substation and connected between one line-limband the third conductor, a second signal-bell adapted to be actuated bypulsating currents located at a second substationand connected betweensaid third conductor and the second line-limb, a direct-currentgenerator at each of said substations adapted for connection in bridgeof the line-limbs, and means whereby the actuation of each generatorautomatically closes a low-resistance path between said third conductorand that line-limb to which the associated signal-bell is not connected.

lei. In a telephone-exchange system,'the combination with a bimetallictelephone line extending by-its limbs-from an exchange to a series ofsubstations, of a signal-bell adapted to be actuated, by pulsatingcurrents located at one substation and connected between one line-limband the third conductor, a second sig-' rial-bell adapted to be actuatedby pulsating currents located at a second substation and connectedbetween said third conductor and the second line-limb, a direct-currentgenerator at each of said substations adapted'for con nection in bridgeof the line-limbs, means whereby the actuation of each generator au-*tomatically closes a low-resistance path between said third conductorand that line-limb to which the associated signal-bell is not connected, and an eIectricaILy -Operated signal device at the centralexchange normally connected in bridge of said line-limbs and adaptedto-be actuated by currents from either of said generators;

In witness whereof I hereunto subscribe my name this 4th day ofNovember,-A. D; 1903.

' GARRISON BABCOCK.

Witnesses:

HARVEY L. HANSON, J QHN STA R.

